1. Field of the Invention
This invention relates to a method of defining the hole position of a part for mounting a punch in design of a progressive mold.
2. Description of the Related Art
In a CAD/CAM system for designing a progressive mold, article arrangement, number of stages, pitch and the like are designed (blank layout processing) conversationally based on an entered article shape, as shown in FIG. 6, then different shapes such as the shapes of a punch and die (DF1-DF3) are designed (strip layout processing). Thereafter, the number and size of plates constituting the progressive mold are defined, the different shapes into which the plates are to be machined and the part holes to be machined are specified (mold conception processing), and finally machining data are outputted for each plate.
A punch and die have a male-female relationship. Therefore, if the shape of one of them is defined, usually the shape of the other is obtained by applying offset processing. Accordingly, punch shape machining data usually are created after the die shape machining data.
However, punch shapes generally are gathered together and subjected to wire-cut machining in such a manner that many punches are obtained from one blank, so as to achieve excellent machining efficiency, without leaving the arrangement of the die shapes as is. FIG. 7(a) is a view showing the positions of die shapes, and FIG. 7(b) is a view showing the arrangement of punch shapes PC1-PC3 in a punch blank WK, these corresponding to the die shapes DF1-DF3, respectively. Therefore, when the punch machining data are created, an offset is applied to the die shapes DF1-DF3 to obtain the punch shapes, and the punch shapes are subjected to translation, rotation, copying, inversion, etc. An arrangement can be adopted in which the punch shapes are obtained by applying the offset after the die shapes are translated, rotated, inverted, etc.
Ordinarily, with a progressive mold, a punch PCH is mounted on a prescribed plate PLT by a bolt BLT, as shown in FIG. 8. Consequently, it is required that holes HL, HL' for mounting the bolt BLT be machined in the plate PLT and in the head of the punch PCH. In designing a part hole in mold conception, holes for mounting bolts, pins or the like fastening the plates together are defined, and the position of the hole HL (FIG. 8) of the part (bolt) BLT for mounting the punch PCH on the plate PLT is defined.
The hole position of the punch mounting bolt BLT in the plate PLT and the hole position in the head of the punch PCH must coincide accurately when the punch is mounted. To this end, when the die shape (punch shape) is moved, as mentioned above, in the creation of the punch machining data, the hole position of the punch mounting part (bolt) is also moved to create the punch machining data, and the part hole HL in the plate for mounting the punch and the part hole HL' machined in the head of the punch are made to precisely coincide.
According to the conventional method, however, the die shape (punch shape) and the punch mounting part hole are moved separately. As a consequence, it is necessary to separately calculate and enter the part hole position after the punch shape is moved. This is a troublesome operation. In addition, there are cases where the positions of the part hole HL in the plate and the part hole HL' in the head of the punch fail to accurately coincide because of calculation error.